fix(badges): keep the medal catalog from being cast to a string on save

user_medal_args was declared as type=json without sanitize_type, so
sanitize_field_value() fell through to sanitize_text_field((string) $value)
and stored the literal string "Array". validate() has no json shape check,
so the save reported success.

Consequence: parse_medal_catalog() json_decoded "Array" into an empty
catalog, the dictionary came back empty, and user_context() dropped every
owned badge — the front end showed "获取徽章" and the grant modal listed
nothing, hiding both the newly added and the pre-existing badges.

Add the missing sanitize_type to match its sibling level/integral fields,
and guard sanitize_field_value() so structured container types can never
reach the scalar fallback again. Mirrors the declaration in the Vue schema.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/Admin/Schema/SchemaUsers.php

@@ -557,6 +557,10 @@ class SchemaUsers {
                                 'key'     => 'user_medal_args',
                                 'label'   => '分类与条目',
                                 'type'    => 'json',
+                                // Must be explicit: sanitize_field_value() only honours sanitize_type
+                                // on the write path. Without it the nested catalog is cast to the
+                                // literal string "Array", wiping every badge from the dictionary.
+                                'sanitize_type' => 'array',
                                 'default' => self::default_medal_args(),
                                 'help' => '结构化目录：分类 → 条目（slug/name/desc/icon/get_type/get_val）。由 SPA UsersBadge 编辑。',
                             ],